Electrical properties of flash-evaporated epitaxial InSb films

Abstract

Amorphous films of indium antimonide (0.02–0.26 μm) and indium arsenide (0.03–0.3 μm) were formed on goldseal glass, freshly cleaved mica and NaCl substrates by using a “flash evaporation” technique. The post-deposition heat treatment was carried out on these films when the amorphous → crystalline transformation was observed. The transformation was characterized by a sudden and large fall in the resistance of the film at a particular temperature depending on the thickness. This transformation was confirmed by transmission electron micrographs and diffraction patterns obtained on the films before and after heat treatment. The transformation temperatures lie between 495–525 K for indium antimonide and 550–575 K for indium aresenide, for the thickness range involved in our investigations. The electrical conductivity measurements showed a temperature dependent activation in the high temperature region and hopping conduction in the low temperature region (Mott's theory). The activation energies, at different temperatures for various thicknesses were calculated and presented. While no Hall mobility could be observed in as-deposited films, very low mobilities were observed in annealed thick films (t > 2000 Å). Thermoelectric power for InSb films was found to vary from 0.075–0.17 mV/K for films of thickness ranging from 1000–2300 Å, whereas for InAs films, its value varied from 0.09–0.27 mV/K for the thickness range, 1250–2500 Å. These measurements indicated the conductivity to be n-type and supported the hopping conduction mechanism observed in low temperature conductivity measurements.